1. Field of the Invention
This invention generally relates to fluid pressure detecting or measuring arrangements of the type in which the fluid whose pressure is being measured is isolated from a pressure-detecting mechanism or gauge and, more particularly, to a temperature-resistant arrangement for measuring the pressure of fluid at elevated temperatures, e.g. above 285.degree. F.
2. Description of Related Art
There are already known various constructions of fluid pressure-detecting or measuring arrangements, among them such in which a flexible elastomeric rubber sleeve isolates or separates a test fluid whose pressure is to be detected from a pressure-detecting mechanism or gauge proper, and wherein a pressure-transmitting fluid is used to transmit the pressure which acts on the rubber sleeve to the gauge. For example, in U.S. Pat. No. 4,534,224 a generally annular housing is interposed between two flanges of a pipe line and connected thereto. An annular flexible rubber sleeve is received in a longitudinal bore of the housing. This sleeve bounds a confining space with the bore, the confining space being filled with a pressure-transmitting fluid, as is a gauge which is in communication with the confining space through a mounting portion thereof which is sealingly received in a port of the housing that opens into the bore.
This known arrangement works quite satisfactorily in many instances in that the pressure of the test fluid that is to be detected acts on the rubber sleeve and flexes the same accordingly, thereby displacing a corresponding amount of the pressure-transmitting fluid out of the confining space and into the gauge which is thus subjected to a pressure corresponding to that to be detected, and thus indicates the same with an accuracy which is determined solely by the construction of the gauge. Moreover, since the inner diameter of the rubber sleeve corresponds to that of the pipe line, there is a smooth transition between the pipe line and the rubber sleeve, thus avoiding corners in the flow path where ingredients of the test fluid could deposit with deleterious effects on the performance of the arrangement. Also, the rubber sleeve separates the test fluid from the gauge, thus protecting the latter, for instance, from attack or clogging by such test fluid. Furthermore, since the rubber sleeve flexes during the use of the arrangement, any deposits or encrustations which may develop thereon are broken up and disassociated from the rubber sleeve, thus not interfering with the flexing of the latter.
However, experience with the arrangement described above has shown that, as advantageous as it may be in many respects, the rubber sleeve tends to become tacky when the test fluid is at an elevated temperature on the order of 285.degree. F. and above. In some applications, for example, the food industry, there is a requirement to steam out and clean the pipe line after a food slurry has been conveyed therethrough. Steaming above 285.degree. F. will adversely affect the rubber sleeve. Also, it has been observed that elevated temperatures will cause the pressure-transmitting fluid to expand outwardly of its confining space, thereby leading to erroneous pressure readings. Hence, there is a temperature limitation on the prior art arrangements employing rubber sleeves as a flexing element.